Annoying, yet valid, WorldBank DOI

[shamess]

The WorldBank has a DOI which ends in a dot.

https://doi.org/10.1596/1020-797X-10_2_7.

Unfortunately, DOI.extract doesn't appear to support that.

[1] pry(main)> Identifiers::DOI.extract('https://doi.org/10.1596/1020-797X-10_2_7.')
=> ["10.1596/1020-797x-10_2_7"]

[jbilbo]

maybe we can add a strict option